An important step in the development of an integrated semiconductor circuit is the development or design, respectively, of the layout. The layout consists of a multiplicity of elemental areas which define the shape and arrangement of patterns of the integrated circuit. As a rule, the patterns are arranged in a number of planes lying above one another in the completed integrated circuit. Correspondingly, the elements of the layout are also attributed or assigned to various planes or layers, respectively. In most cases, an engineer designs the layer manually, supported by software.
An integrated semiconductor circuit can contain a very large number of transistors, resistors, capacitors and other circuit elements. To these are added wiring lines within a number of planes and between these planes. Each of these elements is defined by one, but as a rule by a number of elemental areas of the layout. The operation of all circuit elements and of the integrated circuit overall is dependent on the dimensions of the elemental areas, on their relative arrangement and, in particular, on their dimensions and spacings. For this reason, for example, minimum widths, minimum areas and minimum distances apply, as a rule. If these are not maintained, the patterns are not completely created, for example in lithography steps, or conversely joined to one another by unwanted bridges, or in the case of etching steps, openings in a layer are not completely created or patterns which are too small are completely removed.
To avoid such faults in the production of the integrated circuit, a layout is subjected to an extensive check after having been designed and before lithography masks are produced. As a rule, this check proceeds in two phases. In a first phase, possible faults are identified. This is often done in an automated manner by means of a corresponding software and is also called design rule check. In a second phase, all positions of the layout identified as potential faults are checked and, if necessary, corrected.
As a rule, a layout is subjected not only to a single but to a multiplicity of design rule checks. Design rule checks are used, in particular, for checking the linear dimensions of the elemental areas maintained in the layout for whether minimum distances and minimum widths are maintained.
However, there are other important design criteria, the checking of which leads to an avoidance of faults.